HOWTO : Configure OpenSSH to Fetch Public Keys from OpenLDAP for Authentication on CentOS

Today we will configure our OpenLDAP server to store SSH public keys so that the OpenSSH daemon can fetch them and thus authenticate our users.

To do this, we first need two CentOS machines. This is easy to achieve via a KickStart. If you need help building a KickStart server, follow my previous blog post. Then we need a working OpenLDAP server. If you don't have one, then follow my previous blog posts to set one up.

HOWTO : CentOS 6 KickStart Server

This blog post will explain how to build a Kickstart server which is used to automatically perform untattended OS installation and configuration of both RedHat 6 and CentOS 6 machines.

Kickstart is basically a copy of the Solaris Jumpstart. If you manage IBM AIX machines, it's the equivalent of NIM. Or Ignite in the HP-UX world.

CentOS yum(8) Error « No module named cElementTree » Fixed

I've been having problems with yum(8) on one of the CentOS 6 x86_64 machines. After looking at many different forums and bug reports, I now found the solution.

MySQL Backup and Recovery

If your site manages it's data with MySQL, then you obviously need to make sure the data is safe. In this blog post, I will show how to create a daily backup automatically. I will also show a continuous data protection plan for MySQL databases. This blog post uses the previous backup server configured in my Secure Backup & Recovery with rsnapshot, rssh and OpenSSH article.

Oracle Data Pump

Today I'm going to show how I use Oracle Data Pump utilities. Starting with Oracle 10gR1, Oracle replaced both the export and import utilities by their new Data Pump counterpart : expdp and impdp respectively. The official documentation on these utilities is found in the Oracle Database Utilities10g Release 2 (10.2)

The steps outlined in this blog post are part of a database consolidation effort in which several databases from two different machines will be merged into a new Linux x86_64 server running RedHat Enterprise Linux 5.9 and Oracle RDBMS 10gR2.

Oracle Database 11.2.0.3 Install and Setup on RedHat Linux 6 x86_64

In this post we will install a new server with the latest Oracle Database 11gR2 software (as of this writing, it is version 11.2.0.3). In this example, the new machine is called opus.company.com and the new database instance is called meta.

Howto Recover Lost Cisco Enable Password

In this blog post, we will recover from a lost Cisco switch enable password.

How to remove an FC LUN from a running RedHat 6 server.

This quick howto document shows how to remove a fibre channel LUN under multipathd(8) control from a running RedHat Enterprise Linux 6 machine. Be careful when performing online storage modifications. Make sure you have a valid backup. And of course I can't be held resonsible for any problems if you follow these steps ;)

Secure Backup & Recovery with rsnapshot, rssh and OpenSSH

Overview

Wee all need to backup our machines. But we also need to keep the data private and the backup procedure secured. In UNIX and Linux machines, we need to run the backup operation as root in order to read everything on the machines. But allowing remote connections as the root user is not exactly a good idea. So how to we proceed? We use rsnapshot(1) and rssh(1) together with OpenSSH to secure the whole process. Here's how to do it on CentOS 6.

In case you're running a heterogeneous network, please note that I've successfully configured this process on FreeBSD, PC-BSD, RedHat, Ubuntu, AIX and Solaris servers.

In this example, our backup server is called backup.company.com and is running CentOS 6 while the clients are :

1. The OpenLDAP server alice.company.com that we configured in several other blog posts and running CentOS 6.
2. A workstation machine called charlie.company.com running PC-BSD 9.0 (i.e. FreeBSD 9.0 :)

HOWTO : OpenLDAP 2.4 Replication on CentOS 6.2

We continue our OpenLDAP 2.4 on CentOS 6.2 with a description on how to setup  between two OpenLDAP 2.4 servers. This happens to be the final bullet point in our list of goals :

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

Of course the first thing to do in order to be able to replication our DIT is to have another CentOS machine. So go ahead and install it on a seperate computer. We will continue with our example two machines : alice and bob. Alice is the current OpenLDAP server while bob was the client. At the end of this document, bob will be the second OpenLDAP server. Which in OpenLDAP syncrepl parlance, we have these entities :

• provider : alice.company.com (a.k.a. master server)
• consumer : bob.company.com (a.k.a. replica server)

CentOS Serial Console Server with Digi AccelePort Xem Module

In order to effectively manage UNIX, Linux and Cisco machines from a remote location, one needs to redirect the console to the serial port and hook this to a serial console server. It is also good on a security stand point because all the messages sent to the console are logged on the console server, thus serving in forensic investigations. Ideally, to have even the BIOS at the serial ports, you need to run Oracle/Sun Microsystems or IBM pServers machines. Most newer x86 servers can redirect their BIOS to the serial port. Do it, it's great! With the console server, you have access to everything the server has to offer from the comfort of your office.

HOWTO : OpenLDAP 2.4 Backup & Recovery on CentOS 6.2

This blog post will explain how to backup and restore our OpenLDAP 2.4 server. This is goal number nine.

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

The Maintenance chapter in the OpenLDAP Administrator's Guide on this topic is not very explicit. We hope this blog post will be more helpful.

HOWTO : Kerberos KDC with OpenLDAP 2.4 Back-End and SASL GSSAPI Authentication on CentOS 6.2

We continue our OpenLDAP 2.4 series with goal number 8. Recall that our goals are :

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

In this document, we will learn how to setup our OpenLDAP 2.4 server as a repository for our Kerberos principals. We will also explore how to configure the client machines. Kerberos is a computer network authentication protocol which works on the basis of "tickets" to allow nodes communicating over a non-secure network to prove their identity to one another in a secure manner. Its designers aimed primarily at a client–server model, and it provides mutual authentication—both the user and the server verify each other's identity. Kerberos protocol messages are protected against eavesdropping and replay attacks. Kerberos builds on symmetric key cryptography and requires a trusted third party, and optionally may use public-key cryptography by utilizing asymmetric key cryptography during certain phases of authentication.

HOWTO : OpenLDAP 2.4 NFSv4 Automount Map Repository on CentOS 6.2

We continue our OpenLDAP 2.4 series with goal number 6.

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

In this document, we will learn how to setup an NFS server along with an NFS client which runs autofs(5) version 5. This daemon will fetch his automount maps from our OpenLDAP 2.4 server. The client will then be configured to mount users home directories from the NFS server. All OpenLDAP users DN will be modified to reflect this change. We will also create a central NFS software repository.

HOWTO : OpenLDAP 2.4 sudo Repository on CentOS 6.2

Today we continue with our OpenLDAP series of blog posts. Recall that our goals were :

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

Since goals 1 to 4 are already achieved in previous blog posts, we are now ready to tackle goal number 5 which is to configure OpenLDAP to be a repository of sudo rules. The official sudo website, the sudoers LDAP manual and the sudo LDAP README file are a good place to start.

HOWTO : OpenLDAP 2.4 Users & Groups Management and PAM Authentication on CentOS 6.2

Today we will create and manage users and groups in our OpenLDAP 2.4 daemon running on a CentOS 6.2 machine. Recall our goals :

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.

HOWTO : CentOS 6.2 OpenLDAP 2.4 Setup

This blog post will show how to install and configure OpenLDAP 2.4 on CentOS 6.2.

Goals

1. Install OpenLDAP 2.4.
2. Configure Transport Layer Security (TLS).
3. Manage users and groups in OpenLDAP.
4. Configure pam_ldap to authenticate users via OpenLDAP.
5. Use OpenLDAP as sudo's configuration repository.
6. Use OpenLDAP as automount map repository for autofs.
7. Use OpenLDAP as NFS netgroup repository again for autofs.
8. Use OpenLDAP as the Kerberos principal repository.
9. Setup OpenLDAP backup and recovery.
10. Setup OpenLDAP replication.